Objective : Fc ϒ receptors (Fc ϒ Rs) may play an important role in positive or negative regulation of immune-cell responses and immune-complex (IC) clearance. Mesangial IgG deposition and circulating IgG / IgA- IC in sera are observed in patients with IgA nephropathy (IgA- N). Therefore, the pathological roles of IgG-IC in IgA-N have been discussed. However, several studies have identified Fc ϒ R polymorphisms (Fc ϒ RIIIa and Fc ϒ RIIIb) that determine susceptibility to autoimmune diseases such as systemic lupus erythematosus and rheumatoid arthritis. The objective of the present study was to clarify whether Fc ϒ R polymorphisms influence susceptibility to IgA- N, clinical features or severity in patients with IgA-N. Materials and Methods : Japanese patients with IgA-N (n =124) and healthy controls (n =100) were genotyped for Fc ϒ R polymorphisms (Fc ϒ RIIla-176F or V and Fc ϒ RIIIb NA1 or NA2). The genotyping of these polymorphisms was performed using allele-specific PCR methods. Associations among Fc ϒ R polymorphisms and susceptibility, levels of serum IgG, intensity of glomerular mesangial IgG deposition and pathological severity were analysed. Results : These two Fc ϒ R polymorphisms did not show any significant differences in genotype or allele frequencies between IgA- N patients and healthy controls. None of the Fc ϒ R poly morphisms had any apparent influence on age of onset, serum levels of IgG or mesangial IgG deposition in patients with IgA-N. However, Fc ϒ RIIIa-176V homozygous carriers (V/ V) showed more severe injury than Fc ϒ RIIIa-176F carriers (F / F or F /V) (P< 0.04). Conclusion : The present study showed that polymorphisms of Fc ϒ RIIIa influence the severity of IgA-N in Japanese patients but not the incidence, suggesting that IgG-IC may play important roles in the progression and prognosis of this disease via Fc ϒ Rs.